CLARKE, BENJAMIN, University of Cambridge,UK; and JOHN UNDERHILL, University of Edinburgh, United Kingdom
Abstract: Early Tertiary Stratigraphy of the Fleft Sub-Basin, West of Shetland: Implications for Basin Development Along the Atlantic Margin
A detailed genetic sequence stratigraphy for the early Tertiary sediments of the Flett subbasin is presented, describing a ten sequence subdivision. The dividing marine condensed horizons are biostratigraphically correlatable with similar surfaces in the North Sea. This regional stratigraphy now allows quantitative comparison of sedimentation east and west of Britain. As the sediment flux between the Scottish provenance and offshore basins is almost a closed system, the erosion history of the provenance can be deduced from the sediment flux into the basins. Although less sediment is shed into the North Sea than onto the Atlantic margin, the proportions through time are similar, indicating a large scale control on sediment supply. Sedimentation rates into the Flett sub-basin vary over an order of magnitude on a half million year time scale during the early Tertiary but clearly reach a maximum at 58Ma, closely corresponding to the peak of igneous activity in the British Tertiary Igneous Province.
A previously unrecognised mid-Paleocene unconformity overlying important low degree extensional faults in the Flett sub-basin represents a period of extension followed by uplift and erosion.We present a new model to explain the complex interplay between volcanism, extension, erosion and sedimentation in the Scottish hinterland and this part of the Atlantic margin, ultimately driven by a combination of lithospheric extension and mantle plume activity.
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